tonight on "nightline," the big fat experiment, from big macs to taco supremes, they were prayed to eat fast food every day to see why some people get sick when they gain weight and some don't. we tag along as they pig out on a fast food binge. deep and treacherous canyons, modern day explorers searching for corners of americas where no one has been before and we tag along for a journey into unchartered depths. revenge of the lawn gnomes, they are popping up in front

lawns everywhere. why ceramic men in pointy hats make for a surprisingly big business. good evening, i'll bill weir and for those who salivate at the very sight of a drive-thru window, it sounds like a dream gig or scam. get paid thousands of dollars simply to chow down on greasy burgers or taco combos, once a day, every day for three months. but this was a real dp perexper a jufrpg food binge in the name of science y some people get diabetes or hypertension when they gain and some don't. here is john donvan. >> two sausage buttery burr ti-

>> a number three. >> he goes to the drive-thru. again and again. and again. >> thank you very much. >> and why? for science. dave giocolo is a guinea pig of sorts. back up a few months, put dave in his car and here was the heaad he heard. >> this study includes a short term high coalorie diet and the diet program. >> reporter: offering to pay people to add fat to their own bodies, adding an extra meal each day, 1,000 calories worth of fast food and a lot of people came forward. like dave. a salesman. >> once i got into work i called right away and i tried to e-mail them. >> reporter: for what? research. >> you can see this is x-ray slice through the abdomen where you can see the thick rim of fat around the outside. >> reporter: the doctor wanted to find out why only some people

who gain weight also get diabetes and hypertension and others do not something he could not research by feeding food pellets to lab animals. >> what you learn in rodents does not always translate to people. what you learn in flies and worms won't translate to people. >> reporter: fast food is a perfect food pellet replacement, good for when you want to measure exactly what people are eating. these five restaurants were chosen for the study. >> they have very regulated food content, we know the cal rories and composition of each restaurant. it's an easy and tasteful way to get people extra calories. >> reporter: also a cash incentive, up to $3000 depending how long it took to gain weight. >> it took a month to get approved. >> reporter: dawn is a nurse and when we met her she had actually completed the program. weight gain from 170 pounds in her first week -- >> i had shakes and burgers and

fries -- >> reporter: did you like it? tacos? >> to 186 aeight weeks later. >> reporte >> reporter: she was paid for the effort, including to earn the last 50 losing all of the weight again, which she did buy dieting and a lot of walk exercise like this the hospital guides them through the weight loss. so before dave even started dawn knew that gaining weight fast with a doctor's permission even only sounds easy. it even seemed easy 'first meal. >> a big mac -- >> reporter: large fries? >> it was great. really good. next night went to taco bell and it was wonderful. >> reporter: and again, this is after you have already eaten dinner? >> this is after i've already eaten dinner. >> reporter: but doctor klein could almost predict what she would see next. >> this is not present for them, not easy to stuff your fast every day for a long period of

time. >> reporter: for two weeks it was all right and then i started really feeling awful. i couldn't hardly breathe anymore. vrt. >> reporter: she so is glad it's over and dave, his starting weight 249.9 with a goal of adding 15 or so pounds for the study and he was loving the thought of that. >> reporter: this is like paradise? >> that's why it sounded so good, i eight at mcdonald's, burger king. >> reporter: how do you see the next several months? >> should be pretty easy. >> reporter: this from a guy who start every morning by a breakfast burrito. he then knew the numbers by heart. >> 707 calories. >> reporter: putting down quarter pounders and caught up with him around week four. bleh. how do you feel about week five? >> my knees are aching, my ankles are aching, it's harder to move. >> reporter: he tmetabolism is mysterious thing.

the weight went on slowly. one week he lost a pound. they told him to up the quantities. >> go up to this, to this. >> reporter: around week 11 he stepped away from his burger and showed me. can you feel the weight on your body? where have you put it on? >> here. here. >> reporter: bigger in there? >> stomach is bigger. >> reporter: you feel it? belt had to come out. >> had to buy different pants. >> reporter: you just want this to be over? >> i'm done with it now. >> reporter: except you're not done with it. >> yeah, i can't get out of it now. >> reporter: a few days ago dave fin frishd 249.9 to 268. just over 18 pounds which he now has to lose, helped perhaps by the fact, he says, he's lost his appetite for fast food for a while. i'm john donvan for "nightline" in st. louis. >> all ninthings in moderation. coming up next, where do you go to really be alone in this nation of 300 million people? our team tags along with the

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it is the frontier of a modern day explorer, a vertical world of slick cliffs and sudden drops and deep in the undiscovered depths of america, called canyoneering, hybrid between mountain climbing and cave explorers, places you wouldn't find on any gps. our team strapped on harnesses, risking life and limb to see

never before center rain andse along with them is matt gutman. >> reporter: there is a moment when rock walls soaring on either side -- when you realize there is no way out but down. >> going back that way is not an option. it's that way or nothing. >> reporter: and what follows for a new generation of modern explorers -- the privilege of being the first humans to see this is a gauntlet, frigid water, slippery rappels, skyscraper-high cliffs and this nagging realization that rescue is impossible. >> search and rescue guys can't even get to you fast if they knew where you were in the first place. >> reporter: no cell phones and in the slot not even satellite phones work. >> satellite phones don't even work in the slots.

>> reporter: you could call them the lewis and clark of canyoneering. you're going to places no one has seen, no human eyes have seen. >> that is right. >> reporter: you push the edge. >> every once in a while you get into a pickle and then you learn something new and try not to make that mistake again. >> reporter: it's a sport/activity that includes rappelling, caving and climbing where you knowingly maroon yourself in the bowels of these vertiginous slot canyons. think of the movie where aron rolston cut his own arm off. three main ways people can get killed? >> in a slot canyon, lots of ways to get trapped, hypothermia, get trapped when your ropes don't reach and people die in flash floods. >> reporter: the stars of the film "the last of the great unknown" offered to show "nightline" one of their favorite canyons. >> this is it. going in hot. >> reporter: canyoneering emerged over the last couple of decades from the domain of tiny

sub culture to nearly mainstream. they have explored over 100 u x unexplored canyons which they have the privilege of name nami. >> won't be long before we're simg. >> reporter: how locold does thr get? the geography is changing around us. this is what it's about, looking at the canyon, so narrow, the colors, the light. >> this is stunningly beautiful. this is the kind of things that you find when you're willing to go, push it a bit and look in some of these deep, dark corners. >> reporter: and we're in the water. gaspi ining as the cold seizes bodies. these are called pod holes but they're the size of swimming pools. >> some of these can be 20, 30 feet deep. you never commit the entire party to the pool like this or everybody gets trapped. >> reporter: you send your most

dispensable person -- our senses, the cold, the cathedral canyon walls. lush, even though this is arizona and then our first rappel. more pod holes and more obsta e obstacles. mora pee rappels. we may be the first to ever see this. the canyon opens grandly into this a bigger canyon, lush with a stream running through it. we break to eat something and marvel at how much is still left unexplored. my guess is there are 300 canyons that are probably worth doing in the grand canyon. and we'll die before we ever see them all. it's just too big. >> reporter: before we know it, thunder starts rolling in, bearing the possibility of flash floods. >> almost like clockwork, it's 1:43 and the boomers start it's it's scary because the flash flood comes through there we're in bad shape. and the long, hard slog back up

the hill to safety begins. starting to rain. it's pretty intense lightning. and getting up this hill is hard. what do you think of that, rich? >> big boomers. going to come down. i think i'm glad i'm not in that canyon right now. >> reporter: one of the few times he'll ever admit that. i'm matt gutman for "nightline," bear canyon, arizona. >> very cool. thanks to matt. coming up, fixtures, kings of the flower bed, potential kidnapping targets and the garden variety gnome comes fully armed. we'll take you to the booming business of lawn ornamentation, next. [ male announcer ] you've reached the age where you don't back down from a challenge. this is the age of knowing how to make things happen.

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if it seems unlikely that a ceramic humanoid in a pointy hat could inspire hatred, love and its own liberation movement then you don't know garden gnomes. david wright brings us a new taste on this abiding, lucrative and largely inexplicable appeal of those little lawn ornaments. >> reporter: the lowly sent nells of the suburban garden, creatures so maligned thend to be kidnapped on a regular basis. on youtube a french group called the garden gnome liberation front -- >> i'll never foreme tget my fi mission. >> reporter: they documented their efforts to return the gnomes to the wild. an idea so kooky travelocity built an ad campaign by the. >> i was nabbed by a husband captain and secreted off around the world.

>> reporter: popularity of the germanic garden gnomes inspired a booming business. this is garden gnome central? >> it's everything central. >> reporter: a u.s. navy reservist on his way to afghanistan when inspiration struck. >> some time around 3:00 in the morning standing watch on a bridge, nothing out there except for me and the horizon, started writing notes for different concepts using garden gnomes. >> recon plan charlie. execute. let's move, move, move! >> reporter: he thought about the green army action figures. the ones from "toy story." >> i thought i told him to pick these up. >> reporter: that's when he thought, combat garden gnomes. heavily armed little bearded guys? he sold about 1500 of them at $50 a pop. >> i did a standing rifleman, ne kneeling rifleman, rpg guy, officer with the pistol and sort

of follow me pose. >> reporter: he even has plans for a parachute guy. >> he'll hang from the tree. >> reporter: he'll plan to make special forces garden gnomes. >> hunched down like he's off the beach, mp 5 sub machine gun. >> reporter: field team 6 garden gnome? he's not the only maker to take creative license. you can buy zombie gnomes. perfect for halloween, even zombie gnomes devouring a pink flamingo. quirky garden sculptures are in big demand judging from the sky mall catalog, they command top dollar. who buy this is stuff? welcome to "jurassic park." people like don of burbank, california. his little backyard is crawling with meat eaters and plant eaters. you ever get freaked out coming out here at night? >> no, no, i usually come here to read. i'll sit and it's not ambience,

nice atmosphere. >> reporter: he invites lady friend oefrs to model and make movies. like "dinosaur valley girls" "beauties and the beasts." no wonder he likes his privacy. >> not too many people know what i have. >> reporter: your neighbors don't know they have "jurassic park" next door? >> that's true. >> reporter: it took a while for the business to start but now it's boomg. >> the world doesn't team in armed garden gnomes, turns out after the world found out about them they do. >> reporter: anyone who tries to liberate these little guys getter be prepared for a fight. i'm david wright for "nightline" in petaluma, california. >> must have the zombie gnomes eating the flamingo. thank you, david and thank you for watching abc news. tomorrow night, please join us for kickoff of the special coverage of the presidential debate, the first